In Keys from the Golden Vault, it says:
Many of this book’s heists involve procuring a MacGuffin. Part of preparing for these heists is determining where the MacGuffin in question is located.
If the characters are having too easy of a time finding the MacGuffin, consider shifting its location to another place that makes sense. Or consider revealing that the MacGuffin is a fake, and the real prize is still nearby. The characters should still be able to determine where it’s really located.
[…]
If you use the moving MacGuffin complication, be careful of moving the MacGuffin more than once. Having trouble locating the object of the heist could unduly frustrate your players.
I feel that this text could be easily misread as if it’s OK for the DM to be yanking around the maguffin post-hoc or, and this would be worse: that the writers of the book actually intends for such moving target shenanigans.
That’s messed up.
I recommend sticking to the Paper→Rock principle:
When you play Paper Scissor Stone it’s obviously cheating to act a little bit slowly and select paper after seeing rock. Both people need to select simultaneously.
If you secretly write down your selection in advance, you don’t have to be as precise with the timing. Your selection is committed long before you saw that rock.
Even to the point that it’s enough for one person to write down their selection, as long as they write it down before the other person announces their selection.
Blorb is based on this. That’s why you need to write “this room has 3d6 skeletons” before the players go there. No quantum keeps. You’ve got to let them make real choices.
One of the reasons Curse of Strahd (and I6 before it) strikes such a great balance between shared experience and unique journey is how three big MacGuffins are randomly placed. But, they’re still placed, they’re not willy-nilly moving around.
One of the worst pieces of GM advice I’ve ever seen is this, from How to be a GURPS GM:
The Illusion of Freedom
Regardless of play style, you can often maintain the illusion of player freedom by simply staying flexible as to where and when encounters occur. No matter what the notes say, nothing becomes “real” to the protagonists in the game world until they actually experience it. Up to that moment, the GM can make any changes he likes, assuming they fit the setting and follow logically from previous events.
A classic example is an adventuring party traveling through the wilderness and coming to a fork in the road. Assume the GM has created a small keep as an encounter, complete with some memorable NPCs and a few adventure hooks. If the GM has already told the players the keep is along the left road, or given them a map showing the keep on the left road, then in the game world that’s where the keep is. If they choose to travel the road on the right, there is no logically consistent way they will arrive at the keep.
However, if the keep was not previously mentioned, the GM can place it along whichever road the party chooses to travel – if they go left, it’s along the left road; if they go right, it’s along the right road – and as far as the game world (and the players) are concerned, that’s where it has always been. Similarly, the keep the GM created doesn’t have to be a keep. If the party knows the keep is along the left road, and they choose to travel the right road, perhaps they eventually come upon a crossroads inn, where many of the same NPCs and adventure hooks from the keep now reside.
That’s not cool.
To some, this may seem somehow sneaky or underhanded.
Yeah. It is, de jure, an unblorby way to play.
Not every game needs to be blorby but one of the huge upsides of having a DM is that it enables blorby play. Otherwise you might as well play GM-less games like Fiasco or Mythic or Ironsworn, and that’s not a slam on those games, I’m genuinely glad to see that those playstyles are growing.